xref: /freebsd/usr.bin/truncate/truncate.1 (revision 7aa383846770374466b1dcb2cefd71bde9acf463)
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2.\" Copyright (c) 2000 Sheldon Hearn <sheldonh@FreeBSD.org>.
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26.\" $FreeBSD$
27.\"
28.Dd December 19, 2006
29.Dt TRUNCATE 1
30.Os
31.Sh NAME
32.Nm truncate
33.Nd truncate or extend the length of files
34.Sh SYNOPSIS
35.Nm
36.Op Fl c
37.Bk -words
38.Fl s Xo
39.Sm off
40.Op Cm + | -
41.Ar size
42.Op Cm K | k | M | m | G | g | T | t
43.Sm on
44.Xc
45.Ek
46.Ar
47.Nm
48.Op Fl c
49.Bk -words
50.Fl r Ar rfile
51.Ek
52.Ar
53.Sh DESCRIPTION
54The
55.Nm
56utility adjusts the length of each regular file given on the command-line.
57.Pp
58The following options are available:
59.Bl -tag -width indent
60.It Fl c
61Do not create files if they do not exist.
62The
63.Nm
64utility does not treat this as an error.
65No error messages are displayed
66and the exit value is not affected.
67.It Fl r Ar rfile
68Truncate or extend files to the length of the file
69.Ar rfile .
70.It Fl s Xo
71.Sm off
72.Op Cm + | -
73.Ar size
74.Op Cm K | k | M | m | G | g | T | t
75.Sm on
76.Xc
77If the
78.Ar size
79argument is preceded by a plus sign
80.Pq Cm + ,
81files will be extended by this number of bytes.
82If the
83.Ar size
84argument is preceded by a dash
85.Pq Cm - ,
86file lengths will be reduced by no more than this number of bytes,
87to a minimum length of zero bytes.
88Otherwise, the
89.Ar size
90argument specifies an absolute length to which all files
91should be extended or reduced as appropriate.
92.Pp
93The
94.Ar size
95argument may be suffixed with one of
96.Cm K ,
97.Cm M ,
98.Cm G
99or
100.Cm T
101(either upper or lower case) to indicate a multiple of
102Kilobytes, Megabytes, Gigabytes or Terabytes
103respectively.
104.El
105.Pp
106Exactly one of the
107.Fl r
108and
109.Fl s
110options must be specified.
111.Pp
112If a file is made smaller, its extra data is lost.
113If a file is made larger,
114it will be extended as if by writing bytes with the value zero.
115If the file does not exist,
116it is created unless the
117.Fl c
118option is specified.
119.Pp
120Note that,
121while truncating a file causes space on disk to be freed,
122extending a file does not cause space to be allocated.
123To extend a file and actually allocate the space,
124it is necessary to explicitly write data to it,
125using (for example) the shell's
126.Ql >>
127redirection syntax, or
128.Xr dd 1 .
129.Sh EXIT STATUS
130.Ex -std
131If the operation fails for an argument,
132.Nm
133will issue a diagnostic
134and continue processing the remaining arguments.
135.Sh SEE ALSO
136.Xr dd 1 ,
137.Xr touch 1 ,
138.Xr truncate 2
139.Sh STANDARDS
140The
141.Nm
142utility conforms to no known standards.
143.Sh HISTORY
144The
145.Nm
146utility first appeared in
147.Fx 4.2 .
148.Sh AUTHORS
149The
150.Nm
151utility was written by
152.An Sheldon Hearn
153.Aq sheldonh@starjuice.net .
154